Procedure for 2 SOA records on same IP

What is the proper ispconfig 3 procedure to configure the DNS server for 2 to 5 SOA domain name on the same static IP. Is it better to have 2 servers with two static address? I can only have one soa to work at a time.

Do you need to create 1st soa with ns1.mywebsite.com, ns2.mywebsite,com,
2nd soa with ns3.mywebsite.org, ns4.mywebsite.org
3rd soa with ns5.mywebsite.net, ns6.mywebsite.net and so forth?

Or only one SOA record is allow in ISPconfig and from point to the respective website.